I present you my favorite applications to capture packets on the network, although they are well known for their features, I decided to give a little space to discuss some of their features. In addition to data capture, these applications are useful for certain packets analysis with the obtained data, on the other hand, when the analysis that we need to do is a bit complex or very specific, it is always advisable to build our own scripts, but there is no doubt that no matter for what we use them, this applications will help us to obtain useful network information. This applicacions can also be combined with traffic generators in order to analyze some network issues.
TCPDUMP  is a tool for capturing traffic flowing through the network in real time, this includes packets transmitted and received on a specific network interface. This tool has no graphical interface, this makes for one of the favorite applications when you want to use minimum resources as possible, also be suitable for unattended packet capture, because it can be managed by command line as it can seen in Figure # 1.
Figure # 1: View of the contents of various packets for command line using TCPDUMP.